Traditional approaches for aortic valve replacement require the cutting of a relatively large opening in the patient's sternum (“sternotomy”) or thoracic cavity (“thoracotomy”) in order to allow the surgeon to access the patient's heart. Additionally, these approaches require arrest of the patient's heart and a cardiopulmonary bypass (i.e., use of a heart-lung bypass machine to oxygenate and circulate the patient's blood). In recent years, efforts have been made to reduce invasiveness by using a transcatheter procedure, namely by delivering and implanting a prosthetic valve via a catheter inserted through a smaller skin incision, using either a transvascular route or a transapical route to the valve implantation site. The prosthetic valve (also referred to herein as a stent-valve) comprises a valve component and a stent component for anchoring the valve component at the desired implantation site.
While less invasive and arguably less complicated, transcatheter heart valve replacement procedures still face various difficulties. One issue encountered with a transvascular route is difficulty of navigating, along a tortuous and often stenosed vasculature, a delivery catheter large enough to accommodate a prosthetic valve for implantation. The distal end of the delivery catheter is typically in the range of 6-8 mm in diameter (18-24 French) to accommodate the prosthetic valve. The design of a delivery catheter has to address requirements for (i) atraumatic introduction, navigation and later withdrawal through the vasculature, and (ii) support, for example, for applying force along the length of the catheter from the proximal end, to traverse the existing valve, and manipulate the distal end to unsheath and deploy the prosthetic valve. These requirements often conflict, leading to compromises in design. For example, softness and flexibility of the catheter are desired for autraumaticity and ease of navigation, but reduce the ability of the catheter to provide support for force applied from the proximal end remotely to the distal end.
A further issue is the difficulty of remotely positioning the delivery catheter at an optimum position for deploying the prosthetic valve. If the prosthetic valve is not placed in the proper position relative to the implantation site, it can lead to poor functioning of the valve, or require further surgery to remedy. Incorrect positioning can, for example, lead to one or more complications including: valve regurgitation, instability, valve prolapse, reduced valve aperture, coronary occlusion, mitral valve interaction, and/or heart disfunction requiring the patient to be fitted with a pacemaker.
A further difficulty exacerbating the above is that patients selected for a transcatheter procedure are often those patients not considered suitable candidates for the more traditional, major surgical procedure. For example, such patients may be elderly, frail, suffer one or more morbidities that preclude major surgery and/or that present an unacceptable risk of mortality post surgery. The vasculatures of such patients may be highly calcified, tortuous, stenosed and/or fragile, complicating the process of introducing and advancing the delivery catheter to the implantation site, and increasing the risk of dislodging calcification into the blood stream, and the associated risks of embolisms and even stroke.
The present invention has been devised bearing such issues in mind.